U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ANIMAL I N DUSTRY— Bulletin No. 58. 

D. E. SALMON, D. V. M., Chief of Bureau. 




THE FAT TESTING OF CREAM 



LV THE 



BABCOCK METHOD. 



BY 



ED. H. WEBSTER, Inspector and Dairy Expert, 

DAIRY DIVISION, BUREAU OF ANIMAL INDUSTRY, 
AND 

C. E. GRAY, Special Agent, 

DAIRY DIVISION, BUREAU OF ANIMAL INDUSTRY. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE 
I904. 




Class ' f 2.5 5> 
Book J .___ 



U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ANIMAL I N DUSTRY— Bulletin No. 58. 



D. E. SALMON, D. V. M., Chief of Bureau. 



^9 </- 



THE FAT TESTING OF CREAM 



BY THE 



BABCOCK METHOD. 



BY 



ED. H. WEBSTER, Inspector and Dairy Expert, 

DAIRY DIVISION, BUREAU OF ANIMAL INDUSTRY, 

AND 

C. E. GRAY, Special Agent, 

DAIRY DIVISION, BUREAU OF ANIMAL INDUSTRY. 




WASHINGTON: 

GOVERNMENT PRINTING- Q F.¥ I C E 

1904. : ; ::. 




6 









OCT 20 1906 
D. of 0. 




LETTER OF TRANSMITTAL 



II. S. Department of Agriculture, 

Bureau of Animal Industry, 
Washington, D. C, February 4, 1904. 

Sir: I have the honor to transmit herewith the manuscript of an 
article on "The fat testing of cream by the Babcoek method," pre- 
pared by Ed. H. Webster, inspector and dairy expert, and C. E. Gray, 
special agent, under the direction of Henry E. Alvord, Chief of the 
Dairy Division of this Bureau. Mr. Gray, chemist, of Topeka, Kans., 
was temporarily appointed as special agent to assist in this work. 

It is evident from investigations conducted in the field in connection 
with the gathering of data for this volume that much misapprehen- 
sion exists in regard to the proper waj T of making the Babcoek test 
with cream, and that loose and inaccurate methods of doing the work 
are universally in vogue. This matter becomes of much importance 
when large operations are involved, consequently the information and 
directions submitted in the following pages are of value to creamery 
men and others interested in the subject. I therefore recommend 
the publication of the work as Bulletin No. 58 of the series of this 
Bureau. 

Respectfully, D. E. Salmon, 



Chief of Bureau. 



Hon. James Wilson, Secretary. 

Dy— 51 






CONTENTS 



Page. 

Introduction 7 

A true sample of the cream to be tested 8 

Custom of delivering cream at stations 8 

Thorough uniformity of the cream 9 

Methods of sampling . 10 

Some wrong methods 11 

An exact quantity of the sample in test bottle 11 

Testing after each delivery 12 

The composite sample r j . 12 

Table I. — Effects of evaporation under varying conditions of jar 

covers _ 12 

Measuring or weighing the samples 14 

Reading the test accurately 14 

A comparison of various Babcock tests with the test by ether extrac- 
tion 15 

Table II. — Readings of Babcock tests compared with similar fig- 
ures obtained by ether extraction 16 

Table III. — Summary of average differences between extraction 

and Babcock methods . _ . . . 16 

A comparison of milk and cream readings 16 

Table IV. — Excess of average cream readings A, B, and C over 

milk reading A r 17 

Experiments at the Kansas experiment station 17 

Errors caused by incorrect reading of the meniscus 17 

Table V. — Effect of meniscus in bottles of different diameter 18 

Table VI. — Showing corrected readings after deducting portion of 

meniscus, as per rule 19 

Table VII. — Results of applying rule for reading meniscus to read- 
ings found in Table II . 20 

Table VIII. — Showing average excess of Babcock readings over 

extraction readings ■_ 21 

The lower meniscus ^ 22 

Errors due to expansion by heat 22 

Table IX. — Average readings of six bottles at different tempera- 
tures, showing expansion 23 

Table X. — Average changes in readings at stated temperatures due 

to heat expansion _ _ 23 

Financial results of incorrect reading of tests 24 

Table XI. — Showing losses at cream-receiving stations in Kansas 

and Nebraska, 1902-03 ." 25 

Summary .... 26 

Condensed directions for making tests of cream : 26 

Concluding notes 28 

5 



ILLUSTRATIONS. 



Page. 
Pig. 1. The "Meniscus." Section of a test bottle showing readings of fat 

column from different points of the meniscus l 15 

Plate I. Types of cream and milk test bottles used in experiments 16 

II. Types of cream and milk test bottles, filled, showing fat columns, 
meniscuses, etc 16 

6 



THE FAT TESTING OF CREAM BY THE 
BABCOCK METHOD. 



INTRODUCTION. 



Investigations made during the summer of 1903 among the large 
centralizing creameiy plants in Iowa, Missouri, Kansas, Nebraska, 
and Colorado revealed some surprising facts in regard to the general 
practice of handling the Babcock method in cream testing. It would 
seem that a subject which has had so much attention given it from 
experiment stations and practical creamery men everywhere would 
have been thoroughly familiar to everyone in the creamery business. 
The investigations showed quite the contrary. Men who used the 
test daily were found to be at fault in many particulars, and in some 
instances not the first idea of the principle underlying the method 
seemed to be in the mind of the operator. Much of this has grown 
out of carelessness on the part of the user and much is due to improper 
instruction given for the use of the test as applied to cream. These 
difficulties and the discrepancies resulting therefrom led to a more 
thorough examination of the whole subject of cream testing by the 
method named, and it is the purpose of this bulletin to give the result 
of these investigations. It will be necessary to go over the entire 
field and follow each step in detail to insure any completeness in the 
discussion of this subject. Therefore some things may be repeated 
which may not seem necessary, but there will be enough new, at any 
rate to most users of the test, to make the subject as a whole inter- 
esting. 

It may be stated that a large part of the creamery men are gradually 
departing from the rules for operating the Babcock test as prescribed 
by standard works on the subject. There are various reasons for 
this, but uppermost is the shortage which these creameries are experi- 
encing in the overrun or churn yield. In many cases the test is read 
lower than the instructions would warrant, and in others the methods 
of sampling and measuring the cream into the test bottle are modified 
in one way or another. In practically all cases this is not done with 

7 



8 BUREAU OF ANIMAL INDUSTRY. 

any thought of "robbing the patron," as the phrase is commonly put, 
but it is done with a conviction that present methods are somewhere at 
fault, and the attempt is made to even things up and still give every- 
body his due. 

Instances were found where the creamery, as operated under the 
hand-separator system, was getting considerably less butter from 100 
pounds of butter fat from cream than they had formerly obtained 
from the same measure under the whole-milk system. This seemed 
to indicate plainly that the method of testing was at fault, for it was 
j n stly argued that 100 pounds of butter fat should make the same 
amount of butter, whether bought as cream or as whole milk. 

With this brief introduction to an old but exceedingly important 
question, the manipulation of the test will be described in detail, 
faults will be noted, and better methods suggested. Illustrations as 
to what the results of some practices are in dollars and cents are 
included in order to emphasize the importance of very careful work 
by the man who is doing the testing. 

The three vital points in making a test are: (1) A true sample of 
the cream to be tested; (2) an exact quantity of the sample in the 
test bottle; (3) reading the test accurately. These three statements 
seem simple enough at first glance, but they are more complex in 
actual practice, as man}^ a creamery man has been brought to believe 
when the month's business was checked up. 

A TRUE SAMPLE OF THE CREAM TO BE TESTED. 
CUSTOM OF DELIVERING CREAM AT STATIONS. 

It is the custom of the patrons of the Western creameries to bring 
their cream to the factory or to the cream-receiving station in any 
sort of vessel, from a 1-gallon molasses pail to a 10-gallon milk can. 
The molasses pail may be filled completely full, and the milk can may 
have but 8 to 10 pounds in it. In the one case the pail is so full that 
the cream can not be stirred without spilling, and in the other it is so 
far .down from the top of the can and the cream is spread out so thin 
over the bottom that it is often difficult to get a proper sample after 
it is stirred. These cases are not ideal, but they are given as they 
are found in the field, and it is in the field that the testing is done. 

The territory in which these investigations were made has two 
extremes of weather— hot, sultry, summer days, when the thermome- 
ter hovers around 100° F. in the shade and 125° or 130 c F. on the 
creamery or receiving-station platform ; and the cold, blizzardy days 
of winter., when the station or creamery is the coldest place in the 
country except the back of the buggy in which the patron's can has 
been tied for its ride to the station. These two extremes of weather 
present their problems to the man who is going to sample the cream, 
and they are quite different in character. 



FAT TESTING OF CEEAM BY BAECOCK METHOD. 9 

The cream is received in all kinds of places; it may be in an ideal 
creamery or receiving station ; it may be in the back end of a store of 
some sort, without hot water or heat of any kind ; or it may be on the 
route wagon, with the sampling to be done by the route driver. All 
these methods are in accordance with the facts and have to be 
considered. 

THOROUGH UNIFORMITY OP THE CREAM. 

When the can of cream arrives at the weigh platform, there are 
s-ome things of importance to be noted. If the patron has used water 
to flush or wash out the last of the cream after separating, in most 
cases this water would be in a layer on the bottom of the can. It is 
possible that thorough stirring at the farm would overcome this dim- 
culty, but usually this stirring is not done, and the water is in the 
bottom of the can. The portion richest in butter fat is on top, and 
there is a gradation which varies with every inch of depth from 
this richest' cream down to the water. The cream may be thick 
because of the. great amount of butter fat in it, it maj T be thick 
because it is sour, or it may be thick from age. The first and most 
important thing in getting a true sample in an} T of these cases is to 
make the cream to be sampled uniform throughout in richness and in 
physical condition. If this is not done, the first step has gone wrong, 
and every succeeding step will be wrong just to that extent. The 
final result will be Avrong, and in nearly every case the creamery is 
the loser and the patron the gainer. 

This uniformity of the cream can best be obtained in either of two 
ways — pouring or stirring. It can never be properly done by shaking. 
Pouring from one can to another is the best way to do it. At most 
receiving platforms there is nothing at hand but the ordinary 5, 8, or 
10 gallon milk cans. These cans have a narrow neck and cause a waste 
of time and of cream. They waste time because the cream has to be 
poured slowly, and yet there is always a tendency to hurry, so that a 
little cream is often spilled. Two or more cans should be provided 
for this purpose. They should have straight sides and a top entirely 
open, a good heavy bail, and a large hand-hold near the bottom for 
grasping to tip and empty them. If the cream is to be poured directly 
into cans for shipping, the pouring can should have one side elongated 
like the "nose" of a pitcher or coffeepot. A can of this sort should 
hold either 6 or 12 gallons, so as to give plenty of space to empty a 5, 
an 8, or a 10 gallon can of cream without overflowing. 

If the patron's cans are not filled too full, the uniformity of the 
cream may be insured by using a stirring rod in the patron's can. 
Stir vigorously for a few moments. This rod should be made of good 
heavy wire with a disk of tin from 3-J- to 4 inches in diameter securely 
soldered to the lower end. This disk should have a slight cup shape 
and the rod soldered to the inside center of the cup. A good hand- 



10 BUREAU OF ANIMAL INDUSTRY. 

hold should he hent on the other end of the wire. Make the rod long 
enough to work to the bottom of a 10-gallon can. Stirring is not so 
good as pouring, however, and the safest way is to pour the cream 
and then use the stirring rod a moment in addition. 

These methods will answer the purpose in every case except three: 
(1) The cream ma}' be so thick it will not pour, (2) it may be frozen, 
or (3) it ma} 7 be churned. Warm the thick cream until it will pour. 
If no heat is available for this work, the creamery operator will have 
to make a guess at the richness of the cream, or test it and probably 
overestimate the amount of butter fat it contains. When the cream 
freezes, it is the water which crystallizes out, leaving the richer part 
of the cream in the center of the can. If a test is made of this cen- 
tral portion the result may be from 1 to 20 per cent too high. It must 
be thoroughly thawed out and mixed. When the cream is churned, 
if such cream is received at all, test the buttermilk and estimate the 
butter. 

METHODS OF SAMPLING. 

After insuring a uniform mixture of the cream, there are two 
general methods in use for taking the sample — the dipper and the 
sampling tube. If thorough work has been done in the first step, a 
small portion dipped from the cream will.b.e a fair representative of it. 
A dipper about the size of a No. 10 shotgun shell is the most common 
in use. If the sample is to be tested at once, enough cream s lould 
be taken to make two tests. This insures enough cream for a second 
test should any accident occur to the first. If a composite sample is 
kept, a smaller amount should be taken. 

If the sampling tube is employed, it should be lowered slowly through 
the cream, with the top end open, so that it may fill just as fast as it 
is lowered. When it reaches the bottom, place the thumb tightly over 
the top of the tube and lift it out. The rich cream from the top of 
the can will adhere to the outside of the tube. Instances have been 
noted where the operator rubbed this, or a portion of it, into the sample 
jar. The effect, of course, is to give too high a test. The tube, in 
order to work best, should be hot when it is put into the cream. This 
will help the cream to flow readily into it and will also prevent its 
sticking to the outside, and the general results will be better. Keep 
the tube under a small steam jet, and just before using blow it out 
with steam. This will prevent any cream from the previous test from 
influencing the one about to be made and will insure the tube being 
used hot. In the absence of steam pour hot water through the tube. 
The tube sampler, if properly handled, is the preferable way to secure 
the sample. It takes a proportional part and is the surest to give a 
just result when the cream is not thoroughly mixed. 



FAT TESTING OF CBEAM BY BABOOCK METHOD. 11 



SOME WRONG METHODS. 



The amount of cream used in making up composite samples for a 
large number of patrons runs pretty well up in value when it is com- 
puted. If a half-pint sample is taken for each of 1,000 patrons, 
this is equal to 500 pounds of cream. Each sample will take a lit- 
tle less than 20 c. c. if a full 18-gram charge is used. For 1,000 
patrons this will require 20 pounds of cream, leaving 480 pounds to be 
thrown away because of the corrosive sublimate or other preservative 
added to it. If the average test be 35 per cent, the amount of butter 
fat lost will be 168 pounds, which at 20 cents per pound amounts to 
$33.00 per thousand patrons. Should this occur twice a month, the 
loss per thousand for a month will be $67.20. If there are 10,000 
patrons, as is the case with some creameries in the West, this loss 
amounts to $672 per month, which is well worth looking after. 

Observations in the field were to the effect that in many instances 
samples were dipped from the top of the can without stirring or pour- 
ing; this doubtless checked up with an unpleasant loss for these sta- 
tions at the end of the month. One instance was observed where the 
tube sampler was used without stirring or pouring the cream previous 
to its use; the result would be the same as where the sample was 
dipped from the top of the can. The tube always lets a little run 
back into the can before the weight of the cream is balanced by the 
vacuum created at its upper end; the small amount which thus runs 
back is nearty all water or very thin cream. This water is weighed 
as cream and the patron given credit for it; the sample thus taken is, 
therefore, not a true one and the analysis shows too high a percent- 
age of fat. 

If a tester, b}^ careless methods of sampling, makes his average 
test one-half of 1 per cent too high, the result will be astonishing. 
This amounts to 5 pounds of butter fat per 1,000, and at a creameiy 
making 5,000 pounds of butter per day the loss would be 25 pounds, 
or $5 per day, figured at 20 cents per pound; in a creamery making 
20,000 pounds per day it amounts to $20 per day. Combine this with 
the loss previously mentioned and it means a total loss of over $900 
per month, if there be 5,000 patrons and a make of 20,000 pounds of 
butter per day. These losses have actually occurred in many instances 
at the above ratio per thousand patrons. 

AN EXACT QUANTITY OF THE SAMPLE IN TEST BOTTLE. 

There are two general methods of procedure in practice after secur- 
ing the correct sample, namely, by testing each delivery as it is made, 
or by making a composite sample, which is tested each week or semi- 
monthly, or in some cases only once a month. 



12 



BUREAU OF ANIMAL INDUSTRY. 



TESTING AFTER EACH DELIVERY. 

This is for many reasons a better method than taking a composite 
sample. The cream is in better condition to test. There is no chance 
for loss by evaporation, and an absolute check can be kept upon 
the work each day. The chief objections to it are the extra time 
and greater amount of acid required for doing the work. (Details of 
measuring the sample are taken up after the discussion of the com- 
posite sample, as thej T apply to both alike. ) 

THE COMPOSITE SAMPLE. 

There are several things leading up to the measuring of the sample 
iuto the test bottle which will be considered first, as they have a direct 
bearing on the final result. 

The sample jar. — \Y~hen a composite sample is kept, the sample jar 
is of great importance. It must have a perfectly tight cover to pre- 
vent evaporation. The amount of evaporation that may take place 
is shown by the following data taken from the testing room of a large 
Western creamery: 

Table I. — Effects of evaporation under varying conditions of jar covers. 



Condition of jar cover. 


Quantity of 

cream or 

milk. 


Per cent of fat on— 


Nov. 13. 


Nov. 27. 


Dec. 4. 


Series A. 


e. c. 


Per cent. 


Per cent. 


Pe. cent. 


Tight cover 


35.2 


37.2 


39.4 


40.2 


Do 


70.4 

140.8 

So.2 


38.2 
38.4 
39.4 


38.2 
38.8 
58.6 


39.0 


Do 1 


39.2 


Loose cover _ 


(a) 


Do 


70.4 

140.8 

35.2 


38.4 
38.2 
38.4 


40.2 
39.6 

( a ) 


42.4 


Do .' :.-. 


40.2 


No cover 


( a ) 


Do 


70.4 
140.8 


37.8 
38.6 


51.6 
45.4 


82.8 


Do.. 


50.4 


Series B. 




Tight cover 


35.2 


27.8 


28.8 


29.6 


Do 


70.4 


28.2 


27.8 


29.2 


Do --.- 


140.8 
35.2 
70.4 

140.8 


27.8 
28.2 
27.8 
27.4 


28.0 
31.0 
35.4 
28.4 


27.0 


Loose cover 


34.0 


Do 


41.6 


Do 


33.3 


No cover 


35.2 


28.2 


(a) . 


( a ) 


Do 


70.4 


27.8 


43.6 


80.8 


Do - 


140.8 


28.0 


30,8 


45.3 


Series C. 




Tight cover _ 


35.2 


3.8 


3.8 


3.8 


Do 


70.4 


4.0 


3.9 


3.8 


Do 


140.8 


3.8 


3.8 


3.8 


Loose cover .^ 


35.2 


3.8 


4.4 


4.S 


Do 


70.4 
140.8 


3.8 
3.8 


4.0 
4.2 


4.2 


Do 


4.2 


No cover 


35.2 


4.0 


( a ) 


( rt ) 


Do 


70.4 


3.S 


4.4 


5.4 


Do 


140.8 


4.0 


4.0 


4.5 







a Sample dried. 



FAT TESTING OF CREAM BY BABCOCK METHOD. 13 

The jars used in the above test were the ordinary half -pint sample 
jars used for composite samples. The covers were the "Lightning" 
pattern. The jars classed as " tight cover" were in good repair and 
the covers as tight as such jars usually are. The "loose-cover" 
jars had covers that did not fit well and were left somewhat loose. 
The "no-cover" jars were entirely open. Each jar contained the 
number of cubic centimeters of cream recorded under the heading 
"Quantity of cream or milk." On November 13 the cream was tested 
and put into the bottles. This test is recorded under the date named. 
On November 27 and December 4 the samples were again tested, and 
the records of these tests appear under these dates. 

These data are worthy of considerable study. The covers that were 
supposed to be tight evidently were loose enough to let out some 
moisture. The smaller samples show the greatest loss. Those marked 
"Sample dried" were so dried out that they could not be tested at 
all. The sample jars can not be too carefully looked after, and yet 
it is no uncommon thing to see jars containing samples without cov- 
ers or with very imperfect ones. 

The result of such practices is inevitable. The creamery will lose 
money and will, in all probability, never know how it occurred. 

Preserving the sample. — The average sample in which a preserva- 
tive tablet has been placed shows the weakness of the methods of pre- 
serving that are commonly in vogue. A bright-red spot appears 
where the tablet lay in the bottle, the rest of the cream being in no 
way affected by the tablet. Such a method is a waste of tablets, and 
the cream sample is practically in the same shape it would have been 
had no attempt been made to preserve it. The cream is usually thick, 
or quickly thickens in the jar, and the tablet, although dissolved in 
it, is not mixed throughout the cream. As quickly as the operator 
has time after putting the first cream in a jar, if it is too thick, he 
should warm the bottle to about 100° F., thus bringing the cream to a 
fluid condition and enabling an easy mixture of the preservative and 
cream. Usually the next addition of cream can be quite readily 
mixed with the first. The mixing should be done immediately after 
adding the sample to the jar. All the jars should be looked over at 
the end of the day, and any that have not mixed properly should be 
warmed and shaken up until the mixing is complete. 

In the summer time composite samples will sometimes show a sepa- 
ration into layers, the lower portion being whey and the upper part 
fat and casein. Such samples do not look well, but so far as obser- 
vations go this does not to any appreciable extent influence the test, 
provided they are thoroughly mixed before the sample is taken. In 
the winter season it has not been shown that a preservative other than 
the cold weather is needed. In shaking comijosite samples to mix 
preservative and cream always give a rotary motion to the hand, as 
this causes the cream to flow around the bottle. A violent agitation 
will often churn the contents, thus destroying to a great extent the 
usefulness of the sample. 



14 BUREAU OF ANIMAL INDUSTRY. 

MEASURING OR WEIGHING THE SAMPLES. 

The same precaution used in procuring the sample in the first place 
must be used in getting it ready for measuring into the test bottle. 
Bring the cream to a uniform condition by warming the sample 
100° F. or a little more, then pour from one cup to another a sufficient 
number of times to insure a uniform texture of the cream. Be sure 
that no cream sticks to the side of the sample jar. There will be no 
dried cream if the jar has been tightty covered. If dried cream is 
present the test will not be correct, because some moisture has evap- 
orated. If the cream is lump} 7 , pour it through a fine sieve and press 
the lumps through with the finger, as described in Bulletin No. 100 of 
the Vermont Experiment Station. After pouring the cream until it is 
uniform, measure quickly the desired quantity before any movement 
of fat begins toward the top. If the sample has in any way become 
churned, heat it warm enough to melt the butter fat and very quickly 
mix and measure out the desired amount. The test of such churned 
cream can only be taken as an approximation of the true result. 

There is only one correct way of securing a true sample, and that 
is to Aveigh the cream into the test bottle with a delicate pair of scales 
or balances. Anyone desiring correct results should not use the 
pipette measure for cream. There are too man} 7 conditions entering 
into the problem to make the pipette measure at all reliable. The 
cream, in pouring to get a uniform sample, will incorporate more or 
less air. Very often it is partially sour when received and in this 
condition contains many gas bubbles. The specific gravity varies 
with its richness. Thick and viscous cream may contain large air 
bubbles in its body which do not move readily to the surface. 

Tables for correcting the error due to specific gravity have been 
compiled and are correct for that factor, but they do not and can not 
take into account the other factors, which are often of greater impor- 
tance than the specific gravity. The quantity of cream weighed into 
the test bottle does not matter, so long as the correct reading of the 
result can be obtained. Usually 9 or 18 grams are taken, but some- 
times a less amount is used. 

The details of making the test after weighing out the samples are 
of so common knowledge as to make it needless to discuss them here. 
It is sufficient to say that the desired end is a perfectly clear fat col- 
umn, so that the readings can easily and readily be made. 

READING THE TEST ACCURATELY. 

This seems the simplest step of all, and yet it has been proven the 
hardest. Mention has been made of the fact that creameiy men were 
reading the cream test lower than standard instructions warranted. 
The} r doubtless reasoned that the test must be too high or they would 
get an overrun equal to that obtained under the whole-milk system. 



FAT TESTING OF CREAM BY BABOOCK METHOD. 



15 



Only one creamery in all the territory under investigation had made 
any attempt to discover why. the test seemed to be too high. This 
creamery, through its chemist, whose work along this line is made use 
of in this bulletin, had worked out the table below showing that 
errors of a glaring character were being made in their methods of 
reading the test. There are a number of different types of cream 
bottles on the market, and the tests made were between different types 
of bottles in use at the creamery in question. Those used were the 
30 per cent 9-inch, 50 per cent 9-inch, and 50 per cent 6-inch bottles. 
The first is not in general use, but the last two are 
used quite extensively in Western creamery practice. 



A COMPARISON OF VARIOUS BABCOCK TESTS WITH THE TEST BY 
ETHER EXTRACTION. a 



10 



-cu 
C 



-d 



The tests by the Babcock method were made as fol- 
lows : All bottles were tested for accuracy of gradua- 
tion before using. Three types were used: First, a 
bottle 9 inches in length, graduated to read two-tenths 
of 1 per cent and up to 30 per cent; this type of bottle 
will be referred to as the 30 per cent 9-inch bottle. 
Second, a bottle 9 inches in length, graduated to read 
five-tenths of 1 per cent and up to 50 per cent; this 
type of bottle will be referred to as the 50 per cent 
9-inch bottle. Third, a bottle 6 inches in length, grad- 
uated to read five-tenths of 1 per cent and up to 50 per 
cent ; this type of bottle will be referred to as the 50 
per cent 6-inch bottle. All samples were weighed on 
a Torsion balance, sensitive to 10 milligrams. The 
weights used vere tested for accuracy. All readings 
were taken sli 130° F., this temperature being obtained 
by placing the bottles in water and heating to this 
point. Three readings were taken from each test, the 
method being as follows : Reading A, from a to re- 
reading B, from b to d; reading C, from c to d. 
The crescent-shaped surface of the fat in the neck of 
the bottle, as shown at a b c, is called the meniscus. 

The determination by the extraction method Avas made as follows: 
Samples of about 5-J grams were weighed out into fat-free extraction 
thimbles, charged with ignited asbestos, then dried to constant weight 
at 100° C. The samples were then placed in a continuous ether 
extractor and the extraction carried on with ether that had recently 
been distilled over sodium. After six to eight hours' extraction the 
flasks containing the extracts were removed and replaced by other 
flasks and the extraction again continued for three hours. This 
extraction gave only a trace of fat. The extracted fat was dried to 



Fig. 1.— The "Me- 
niscus." Section 
of a test bottle 
showing r e a cl- 
ings of fat col- 
umn from differ- 
ent points of the 
meniscus. 



« Tests made by C. E. Gray 



16 



BUREAU OF ANIMAL INDUSTRY. 



constant weight at a temperature of 100° C. Duplicate analyses were 
made of all samples. Only the averages are given in the table below: 

Table II. — Readings of Babcock tests compared with similar figures obtained by 

ether extraction. 



Sample. 



No.l _ 


No.2 


No. 3 


No. 4 . 


No.5 


No.6 




No. 7 



Result by 
ether ex- 
traction. 



Per cent. 
52.32 

43.41 

39.28 

26.23 

23.42 

8:27 
8.30 



Results by Babcock method. 



Reading. 



30 per cent 

9-inch 

bottle, 

9-gram 

sample. 



50 per cent 50 per cent 

9-inch 6-inch 

bottle, bottle. 

18-gram ; 18-gram 

sample. sample. 



Per cent. 

52.90 

52.50 

52.00 

44.201 

43.80 

43.40 

39.80 

39.40 

39.00 

27.00 

26.60 

26.20 

23.90 

23.50 

23. 10 

8.80 

8.40 

8.00 

9.00 

8.60 

8.20 



Per 



cent. 

53.20 

52.80 

52.35 

44.10 

43.70 

43.30 

39.75 

39.25 

38.75 

26.80 

26.30 

26.00 

23.90 

23.45 

22. 95 

8.80 

8.45 

8.05 

9.00 

8.65 

8.35 



Per 



rent. 

53.85 

53.10 

52.40 

44. 45 

43.80 

43.25 

40.00 

39.40 

38. 75 

27.15 

26.60 

26.05 

24.20 

23.80 

23.40 

9.55 

8.90 

8.25 

9.05 

8.65 

8.25 



Table III. — Summary of average differences between extraction and Babcock 

methods. 

[( + ') denotes readings above and ( — ) readings below those obtained by" extraction method.] 



Babcock readings. 



A 
B 
C 



30 per cent 50 per cent 50 per cent 
9-inch. 9^inch. 6-inch. 




The differences in readings of 9-gram samples were doubled in order 
that they should appear in such form as to compare with the other 
columns of the table, which represent 18-gram samples. 

A COMPARISON OF MILK AND CREAM READINGS. 

The lowness of the milk test as compared with cream readings is 
exemplified by the following table, which gives the summary of dif- 
ferences as compared with the test made in the 10 per cent milk bottle. 



Bulletin No. 58, B. A. I. 



Plate I. 



< 



O 
jo 
m 
> 



H 
m 



C 

03 

m 
o 



m 

X 

m 

m 

z 
H 




Bulletin No. 58. B. A. I. 



Plate II 




JO 



? 



FAT TESTING OF CREAM BY BABCOCK METHOD. 



17 



The readings were made and the differences found in the same man- 
ner as in the comparison with the ether extraction figures, shown in 
Table III. 

Table IV. — Excess of average cream readings A, B, and C over milk reading A. 



Cream reading. 



A 
B 
C 



30 per cent 
9-inch. 



-}-0. 51 
+ .27 
+ .07 



50 per cent 50 per cent 



9-inch. 



6-inch. 



+0.&5 
+ .32 
+ .05 



+1.50 
+ .75 
+ .20 



Credit is due to Mr. Gray for suggesting this line of investigation. 



l && 



A careful study of the foregoing tables will indicate that something 
wrong is pretty sure to occur when the Babcock test is applied to 
cream by a careless or inexperienced operator. The readings were 
made at a, b, and c in the above work because these points were quite 
distinct and could be read without much chance of error. The results 
show that the probable cause of the differences in the readings of the 
different types of bottles lies in the meniscus. (See fig. 1, p. 15.) Fol- 
lowing out this suggestion, a series of experiments were undertaken at 
the Kansas Experiment Station. 

EXPERIMENTS AT THE KANSAS EXPERIMENT STATION. 

Through the courtesy of Prof. J. T. Willard, director and chemist 
of the Kansas station, Manhattan, Kans., the author secured the use 
of the station chemical laboratory and the cooperation of the assistant 
hemist, Mr. R. H. Shaw, in carrying on further the work already 
< lined. Prof. J. O. Hamilton, assistant professor of physics in the 
Kansas State Agricultural College, gave material assistance in the 
mathematical and physical problems involved. Experiments were 
repeated with the same results as obtained in the work already quoted 
and shown in Tables II, III, and IV. 

ERRORS CAUSED BY INCORRECT READING OF THE MENISCUS. 

The most interesting feature of the work was a study of the effect 
of the meniscus in bottles of different diameters on the reading of the 
test. A series of thirteen bottles were selected ranging in diameter 
of neck from 0.2338 inch to 0.5862 inch. The bottles were filled with 
water to some point in the lower part of the neck, and then 1 gram of 
pure butter fat weighed into the neck. The specific gravity of the 
fat was 0.9, and each gram should represent just 5.55 plus per cent 
butter fat. .The bottles were whirled in a hand tester and read at 
120° F. Readings from extreme top to bottom of fat column were 
carefully made and the depth of meniscus measured and recorded in 
per cent of the scale on which the reading was made. The following 
2218— No 58—04 2 



18 



BUREAU OF ANIMAL INDUSTRY. 



table gives the style of bottle, diameter of neck, the per cent of fat> 
the depth of meniscus in same terms as fat, and the difference from 
the true amount: 

Table V. — Effect of meniscus in bottles of different diameter. 



Style of bottle. 



10 per cent milk 

30 per cent 9-inch cream 

50 per cent 9-inch cream 
40 per cent 6-inch cream 

50 per cent 6-inch cream 



No. of 
bottle. 


Diameter 
of neck. 


Per cent 
of fat. 


Per cent 
meniscus. 


Difference 

over true 

amount 

(5.53+). 


I 13 


0. 2.338 


5. 70 


0.20 


0.15 


I 12 


.2682 


5.80 


.30 


.25 


[ 3 


.2858 


5.90 


.40 


.35 


42 


.3056 


5.90 


.50 


.35 


5 


.3204 


6.00 


.50 


.45 


I 7 


.3356 


6.10 


.60 


.55 


f 34 


.3916 


6.25 


.80 


.70 


1 32 


.4100 


6.25 


.90 


.70 


f " 45 


.5016 


6.75 


1.50 


1.20 


I 44 


.5232 


♦7.00 


1.80 


1.45 


f 25 


.5498 


7.00 


2.00 


1.45 


J 20 


.5664 


7.25 


2.25 


1.70 


I 19 


.5862 


7.40 


2.25 


1.85 



It will be seen in the above table that the 10 per cent milk bottles 
give a reading of 5.70 and 5.80, respective^, and that the 50 per cent 
6-inch cream bottles give a reading of 7.00, 7.25, and 7.40, and that 
the meniscus of the 10 per cent bottles is 0.20 and 0.30, while for the 
50 per cent 6-inch bottles it is 2.00, 2.25, and 2.25, and, further, that 
the 10 per cent bottles read 0.15 and 0.25 above the true amount and 
the 50 per cent 6-inch bottles read 1.45, 1.70, and 1.85 above the true 
amount. This is especially interesting from the fact that all of these 
bottles have been supposed to read alike. It will also be seen that 
the 10 per cent bottles read more than the true amount, Avhereas in 
general practice the reading of these bottles is supposed to indicate 
the amount exactly; In ordinary milk testing it is estimated that 
about two-tenths of 1 per cent adheres to the inside of the bottle 
below the neck, and in reading the per cent of fat the total leugth of 
the fat column will just give the desired reading. In the above table 
the fat was weighed into the neck of the bottle and. was therefore 
known to be all in the neck, and the effect of the meniscus is thus as 
apparent in the 10 per cent bottles as with the others. 

If we calculate that about the same amount of fat is held back in 
the bulb of all bottles, regardless of size of the neck, it will be seen 
that the differences — as shown in the last column of the above table — 
regularly increase as the necks of the bottles increase in diameter. 
Taking No. 13, the first bottle in the table, as a standard, the differ- 
ences from the true amount, here taken as 5.70, are seen to range 
from 0.10 in bottle No. 12 to 1.70 in bottle No. 19. 

This shows the actual errors that would constantly be made in 
regularly testing with these bottles. 



FAT TESTING OF CREAM BY BABCOCK METHOD. 



19 



Table V shows that the depth of meniscus increases with the diam- 
eter of the neck, and that the true reading comes somewhere between 
the reading of the top and the reading at the bottom of the meniscus. 
A careful inspection of Table V will show that if from the depth of 
the meniscus there is deducted four-fifths of itself, the result will be 
very near the true difference in reading between that which the bottle 
actually gives and the true amount. Therefore the shortest rule that 
can be given to correct the error due to the meniscus is as follows: 
Read the test from the extreme top to bottom of fat column; deduct 
from this reading four-fifths of the depth of the meniscus, and add 
0.2 per cent to the result. The 0.2 per cent is the amount supposed 
to adhere to the test bottle and is not shown in the fat column in the 
neck. In none of the cases in the table will this rule give exactly the 
right figure, but the differences are all, with one exception, less than 
one- tenth of 1 per cent. 

Table VI. — Showing corrected readings after deducting portion of meniscus, as 

per rule. 



Style of bottle. 



10 per cent milk '. 



30 per cent 9-inch cream 

50 per cent 9-inch cream 
40 per cent 6-inch cream 

50 per cent 6-inch cream 

Average 



Number 
of bot- 
tle. 



VS 

12 

3 

42 

5 

7 

34 
32 
45 
44 
25 
20 
19 



Read- 


Depth 
of 


Four- 
fifths of 


ing. 


menis- 


menis- 




cus. 


cus. 


Percent. 


Percent. 


Percent. 


5.7 


0.20 


0.16 


5.8 


.30 


.24 


5.9 


.40 


.32 


5.9 


.50 


.40 


6.0 


.50 


.40 


6.1 


.60 


.48 


6.25 


.80 


.64 


6.25 


.90 


.72 


6.75 


1.50 


1.20 


7.00 


1.80 


1.44 


7.00 


2.00 


1.60 


7.25 


2.25 


1.80 


7.40 


2.25 


1.80 


6.40 


1.07 


.86 



Reading 
less four- 
fifths of 
menis- 
cus. 



Reading 
less four- 
fifths of 
meniscus 
+ 0.2 per 
cent. 



Per 



cent. 
5.54 
5.56 
5.58 
5.50 
5.60 
5.62 
5.61 
5.53 
5.55 
5.56 
5.40 
5.45 
5.60 



5. 54 



Per cent. 
5.74 
5. 76 
5.78 
5.70 
5.80 
5.82 
5.81 
5.73 
5.75 
5.76 
5.60 
5.65 
5.80 



5.74 



If the 10 per cent bottles are taken as correct and as standards in 
this case, the final average is only 0.01 per cent less than the average 
reading of the 10 per cent bottles, the latter being 5.75 per cent. 

If a 9-gram sample is used and the result must be doubled, the 0.2 
per cent must not be added until the four-fifths meniscus is deducted 
and this result multiplied by 2. 

The differences shown in Table VI occur because it is a practical 
impossibility to read the exact amount in any test. In the 10 per 
cent bottles and the 30 per cent 9-inch bottles tenths have to be 
estimated; in the 50 per cent 9-inch bottles anything less than 0.5 



20 



BUEEAU OF ANIMAL INDUSTEY. 



per cent has to be estimated; in the 40 per cent 6-inch bottles used 
in this test anything less than 1 per cent has to be estimated; and in 
the 50 per cent G-inch bottles used anything less than 0.5 per cent 
has to be estimated. All of this estimation makes not only possible 
but altogether probable errors in reading which range from less than 
0.1 per cent to as much as 0.5 per cent. The space occupied by 1 
per cent in the large-diameter bottles is so shallow that a slight tip- 
ping of the bottle away from the perpendicular may easily make a 
difference of from 0.25 per cent to 1 per cent in the reading. 

Applying the rule for reading the meniscus to the readings in 
Table II, the following is the result: 

Table VII. — Results of applying rule for reading meniscus to readings found in 

Table II 



Num- 
ber of 
sample 



Style of bottle. 



130 per cent 
50 per cent 
50 per cent 
130 per cent 
50 per cent 
50 per cent 
130 per cent 
50 per cent 
50 per cent 
130 per cent 
50 per cent 
50 per cent 
130 per cent 
50 per cent 
50 per cent 
130 per cent 
50 per cent 
50 per cent 
(30 per cent 
50 per cent 
[50 per cent 



9-inch . 
9-incli . 
G-inch . 
9-inch . 
9-inch . 
6-inch . 
9-inch . 
9-inch . 
6-inch . 
9-inch . 
9- inch . 
6-inch . 
9-inch 
9-inch . 
6-inch 
9 inch 
9-inch 
6-inch 
9-inch 
9-inch 
6-inch 



Read- 
ing, a 


Menis- 
cus. 


Pour- 
fifths of 

me- 
niscus. 


Per cent. 


Per cent. 


Per cent. 


26.45 


0.45 


0.36 


53.20 


.85 


.68 


53. &5 


1.45 


1.16 


22 10 


.50 


.40 


44.10 


.80 


.64 


44.45 


1.20 


.96 


19.90 


.40 


.32 


.39. 75 


1.00 


.80 


40.00 


1.25 


1.00 


13.50 


.40 


.32 


26.80 


.80 


.64 


27.15 


1.10 


.88 


11.95 


.40 


.32 


23.90 


.80 


.64 


24.20 


.95 


.76 


4.40 


.40 


.32 


8.80 


.75 


.60 


9.55 


1.30 


1.04 


4.50 


.40 


.32 


9.00 


.65 


.52 


9.05- 


.80 


.64 

i 



Reading 
less four- 
fifths of 
menis- 
cus. 



Per cent. 

26.09 

52.50 

52.69 

21.70 

43.46 

43.49 

19.58 

38.95 

39.00 

13.18 

26.16 

26.27 

11.63 

23.26 

23.44 

4.C8 

8.20 

8.51 

4.18 

8.48 

8.41 



Double 
reading. 



Per cent, 
52.18 



43.40 



39.16 



26.36 



23.26 



8.16 



8.36 



+0.2 per 
cent. 



True 
reading 
(by ex- 
trac- 
tion). 



Per 



cent. 
52 32 

43.41 

39.28 

26.23 

23.42 

8.27 
8.30 



a This column gives the highest reading (A) in each case. 

In the above table the column headed " Reading" is the extreme 
reading, and the column headed "Meniscus" is the difference 
between "a" and " c," as shown in fig. 1 (on p. 15). For the 30 
per cent 9-inch bottles only one-half the amounts given in Table II 
are used, as one-half is equal to the 9-gram reading that was taken 
in this case. This is corrected to the proper amount in the column 
headed "Double reading." The column " +0.2 per cent" gives the 
corrected reading, and the column "True reading" gives the amount 
determined by the extraction method. 



FAT TESTING OF CREAM BY BABCOCK METHOD. 



21 



A rearrangement of the final results in the above table makes the 
following showing. The sum of the seven samples is taken and the 
average differences determined : 

Table VIII. — Showing average excess of Babcock readings over extraction 

readings. 



Style of bottle. 



Are: age ; 
reading n „ 

cent ad- 
dition. 



less four 
fifths of 
menis- 
cus. 



30 per cent 9-inch 
50 per cent 9-inch 
50 per cent 6-inch 



Per cent. Per cent. 



28.69 
28.71 
28.83 



0.20 
.20 

.20 



Cor- 
rected 
reading. 



Per cent. 
28.89 
28.91 
29.03 



Average 
true 

amount. 



Per cent. 

28.74 
28.74 
28.74 



Average 
differ- 
ence. 



Per cent. 
+0.15 
+ .17 
+ .29 



The column "Average reading less four-fifths of meniscus" is the 
average of double the 30 per cent 9-inch readings, and the 50 per 
cent 9-inch and 50 per cent 6-inch readings. To these is added the 
0.2 per cent for the corrected reading. From the corrected reading 
is taken the average true amount, which gives the difference found 
in column "Average differences." This is the average above the 
true amount for each reading "A" in the three classes of bottles rep- 
resented in Table II. It is doubtful in making these readings in 
Table II whether the meniscuses were read deep enough, as they were 
not read with a thought of this comparison in view. 

Another possibility enters into the proposition that will have to be 
left an open question for the time being; that is, whether 0.2 per cent 
is not too much to allow for the fat which does not rise into the neck 
when testing cream in the wide-necked bottles. In Table VI it must 
be remembered that the fat was weighed into the neck of the bottle, 
and that the amount was positively known to be in the neck. The 
table Avas arranged from Table V, with the supposition that 0.2 per 
cent would remain below the fat column in all the bottles, and that 
being the case, the assumption that in the 10 per cent bottles the read- 
ing would actually be the same as if the test had been made in the reg- 
ular way and read 5.7 per cent for No. 13, etc. While this is true for 
the 10 per cent; bottles, it may not be true for the cream bottles, as 
Table VIII would seem to indicate. In view of the fact that nearly 
every error in sampling and making tests tends toward a larger read- 
ing than the correct one, the addition of the 0.2 per cent might safely 
be omitted and no injustice done to either party of the transaction. 

It is a common practice to use a 9-gram charge and double the read- 
ing. This multiplies the error made in reading by 2. An examina- 
tion of the diameter of the bottles given in Table V will show the wide 
variations to be found in bottles of the same class. The 13 bottles 
used in this experiment were selected from 50 bottles taken- at random 
from a large stock, and they show almost every grade of variation. 



22 BUREAU OF ANIMAL INDUSTRY. 

It would not be a safe rule to deduct a certain amount from bottles 
of the same per cent reading, the differences between bottles of the 
same class being as great as between classes. 

THE LOWER MENISCUS. 

Among other things observed in making this test was the lower 
meniscus or line between the fat and the liquid below. When the 
bottles were whirled for live minutes in a tester in which the tem- 
perature remained constant, the line between the fat and water was 
a straight line. Immediately on cooling this line began to have a 
curved shape, the center being lower than the sides. If the bottles 
were placed in a hot bath and the temperature raised above that at 
which they had been whirled, the line curved upward, the center 
becoming higher than the sides. These changes in the shape of the 
bottom line, or plane of division, were nearly equal in effect to the 
upper menfscus. If the line curved either wa} 7 , the effect was to 
increase the reading. The curve downward, due to cooling, did not 
affect the reading as much as the curve upward, due to heating. As 
the fat is drawn down and the bottom reading made lower, the fat 
column is shortened at the top, and this in a measure equalizes the 
error. AVhen the center is moved upward as the result of expansion, 
the top is pushed up and the bottom line remains the same; the line 
that touches the glass is then the one from which the reading will be 
taken. This effect has been observed where a hand tester had a 
steam connection for heating the bottles. The operator would turn 
in the steam for the last whirling of one minute and then read the 
test. This sudden heating caused an expansion, and the movement 
of the fat and liquid on the surface of the glass being slower than 
that in the center, the bottom line of the fat column was curved 
upward, and consequent!} 7 the reading was too high. 

ERRORS DUE TO EXPANSION BY HEAT. 

In testing cream the matter of expansion of the fat is of consider- 
able importance. An experiment made by Mr. Gray is here recorded 
which shows the effect of expansion in heating the fats to tempera- 
tures ranging from 110° to 140° F. 

Plan of test. — A sample of pure butter fat was separated from pure, fresh 
butter. A determination of the specific gravity of this fat showed it to be normal 
(0.9004 at 100° C.) compared with water at the same temperature. Samples of 
the fat were weighed into the various types of test bottles and skim milk enough 
added to each to make 18 grams. The fat and skim milk were mixed as thor- 
oughly as possible and the test made as with cream. From this mixture a test 
was obtained that in appearance was very similar to the regular cream test. 
Three readings were taken from each test [as described in fig. 1 (p. 15)]. at tem- 
peratures of 140°, 130°, 120°, and 110° F. Six tests were made with each type of 
bottle, and the results averaged as in the following table. The correct amount is 
very near 39.8 per cent. (That is, this would be the accurate reading or test for 
the fat actually present in this mixture or unnatural cream.) 



FAT TESTING OF CREAM BY BABCOCK METHOD. 



'23 



Table IX. — Average readings of six bottles at different temperatures, showing 

expansion. 



Style of bottle. 



Reading. 



30 pei- cent 9-inch, 9-gram j-JB 

I'C 

f A 
30 per cent 9-inch, reading doubled <B 

[c 

fA 

50 per cent 9-inch. 18-grani 



50 per cent 6-inch, 18-gram. 



Temperatures. 



140° F. I 130° F. 120° F. 110° F 



Percent. Percent. Per cent. Per cent. 



20.1 
19.9 
19.7 
40.2 
39.8 
39.4 
39.9 
39.4 
38.9 
40.5 
39.9 
39.0 



20.0 
19.8 
19.65 
40.0 



39.6 


39.3 


39.7 


39.3 


38.9 


40.3 


39.8 


38.9 



19.9 

19.75 

19.65 

39.8 

39.5 

39.3 

39.5 

39.2 

38.8 

40.1 

39.6 

38.7 



19. 85 

19.75 

19.65 

39.7 

39.5 

39.3 

39.5 

39.1 

38.7 

39.9 

39.5 

38.6 



Tajble X. — Average changes in readings at stated temperatures due to heat 

expansion. 



Temperatures. 



Style of bottle. 


140° to 130° F. 


130° to 120° F. 120° to 110° F. 1 140° to 110° F. 


30 per cent 9-inch, 9-gram 


Per cent. 

0.1 

.2 

.2 

.2 


Per cent. Per cent. 
0. 1 0. 05 


Per cent. 

25 


Same, doubled . . . 

50 per cent 9-inch, 18-gram 


.2 
.2 

.2 


.1 
.0 
.2 


.5 

4 


nd ppT nsnt fi-infh, 18-gra.m 


fi 






Average full reading ... 

Theoretical difference 


.2 

.142 

.071 


.2 
.142 

.071 


.1 

.142 

.071 


.5 

.427 


Same. 9-gram .. 


.213 







The average increase in reading when the temperature is raised 
from 110° to 140° is 0.5 per cent, as taken from the readings in Table 
IX. The theoretical increase is 0.427 per cent. The difference 
between the practical reading and the theoretical calculation is but 
0.073 per cent, which is less than can be read in either of the st3 T les 
of bottles in the test. The coefficient of expansion of fat is given as 
0.00064 for melted butter fat within the range of temperatures as found 
in common testers in use. For each change of 10° F. 1 c. c. of fat, or 
5 per cent, will change 0.0178 per cent. In the above illustration there 
was 39.8 per cent, or nearly 8 c. c. of fat, and the change would be 
eight times 0.0178 per cent, or 0.142 pei cent, as shown in Table X. 
Fifty per cent cream would be ten times 0.0178 per cent, or 0.178 per 
cent. Thirty per cent cream would be six times this factor, etc. 

The correct temperature for reading is given as 120° F., and in 
Table IX the readings, taken at 120° and corrected by the rule for 



24 BUREAU OF ANIMAL INDUSTRY. 

calculating the correct reading, give results nearest to the true amount, 
39.8 per cent. 

It will be seen that the differences of reading, when 9 grams of cream 
are used, are just one-half of those from a full charge, or 18 grams, 
so far as temperature is concerned. It will also he seen that when 
the readings of the 9-gram charge are multiplied by 2 to obtain the 
correct reading, the difference is also multiplied by 2, and the final 
result is the same as though 18 grams had been nsed. There has 
been an objection raised against the long-necked cream bottle to the 
effect that so long a column of fat necessarily shows more expansion 
and greater care must be exercised to have the temperatures just right. 
A careful consideration of the expansion table above will not bear out 
this assertion. Butter fat expands volumetrically. Cream-test bot- 
tles are graduated volumetrically and will take care of any expan- 
sion, no matter what the shape of the neck. With the long scale 
and the narrow neck the expansion is measured in just the same pro- 
portion as in a short scale and wide neck. 

The hand tester will, as a rule, give nearer the right results than 
the steam-turbine tester, because the fat from the hand tester is 
usually read nearer 120°. The steam machine may heat the bottles 
to 160° or 180° F., and if read at this temperature a little calculation 
will show the nature of the results. If the steam machine is run with 
the lid raised an inch or two, better results will be obtained. This 
will allow an air current to be drawn through the machine, and the 
temperature will thus be kept down. If bottles are placed in a water 
bath to bring them to the right temperature for reading, they should 
remain in the bath for twelve to fifteen minutes before being read to 
insure an even temperature of fat and liquid bolow the fat and to 
insure a straight line between the two. 

FINANCIAL RESULTS OF INCORRECT READING OF TESTS. 

It has been stated before that a difference in test of one-half of 1 
per cent would amount to $1 for every 1,000 pounds of butter made if 
valued at 20 cents per pound. In the preceding discussion it is 
shown that in the matter of reading the test alone a difference of 1. 7 
per cent can be made. Figured on the same basis as the above, this 
would equal $3.40 per 1,000 pounds, or $68 per day on an output of 
20,000 pounds. 

The methods of operating and the basis of paying fcr butter fat in 
the centralizing plants give the farmer all there is in it. In other 
words, the farmer in most cases gets a price for a pound of fat or the 
cream containing it which, together with the transportation charges 
on this cream, will equal the selling price of a pound of butter. The 
creamery must make its profits and pay its running expenses out of 
the overrun it is able to obtain. If this overrun is cut down through 



FAT TESTING OF CREAM BY BABCOCK METHOD. 



25 



mismanagement of any kind, profits are gone. Instances are now on 
record where concerns have become bankrupt through bad manage- 
ment along these very lines. The test question is but one item in 
the way of successful operation, and the things pointed out in this 
bulletin are not all the corners that must be watched in getting a 
proper overrun; but so far as the testing goes, this bulletin points 
out the dangers which are of vital importance to the creamery 
manager. 

The following are examples of shortages occurring on several 
systems in Kansas and Nebraska largely due to improper methods of 
testing : 

Table XI. — Showing losses occurring at cream-receiving stations in Kansas and 

Nebraska, 1902-03. 



Month. 



1902 

June.. 

August 

September 

October 

November 

December 

1903 

May 

June 

July 

September 

Do 

July 

August 



Stations. 


Butter fat 

received 

at factory. 


Number. 


Pounds. 


174 


572,936 


179 


481,216 


178 


399,276 


175 


239,847 


175 


191,038 


164 


173,692 


109 


377,576 


177 


812,871 


181 


655, 691 


192 


439,073 


21 


64,326 


259 


794,670 


257 


761,055 



Butter fat 
paid for. 



Pounds. 
581,424 
483,612 
396,575 
244,816 
197,672 
181,598 

392,891 
817,903 
657,806 
439, 886 
69,550 
812,303 
777,486 



Loss. 



Pounds. Per cent. 



2,396 

« 2, 701 

4,969 

6,634 

7,906 

15,315 

5,032 

2,115 

813 

5,224 

17,633 

16,431 



1.45 
.49 
a. 67 
2.03 
3.35 
4.35 

3.89 
.61 
.32 

.18 
7.49 
2.17 
2.10 



a Gain. 

One-half of 1 per cent is allowed for mechanical loss by some of the 
larger creameries. Out of the 1'3 cases represented above, there are 
four within this limit — one showing a gain of 0.67 per cent and one 
very close to the limit. 

The butter fat paid for and the butter fat received are found by 
testing at the station and at the factory. When this was checked 
against a low churn yield, this and the difference between the test 
called for an investigation. Not all of it can be laid to any one thing, 
but with careless sampling, loss of cream by spilling, etc., reading the 
test at too high a temperature, and reading the full meniscus, the 
losses may be found. The differences between the station and the fac- 
tory tests are in the main due to poor work in sampling and testing 
at the station. It is a noteworthy fact that the tests at the factory 
are made more carefully than those at the stations. The station tests 
%s a rule are made by pipette rather than scales. In most cases a cor- 



2(3 BUREAU OF ANIMAL INDUSTRY. 

rection table is used to correct the errors made by pipette measure. 
Although this method gives lower results than with the scales, the 
faulty methods of sampling, combined with too high reading, still 
give the station a higher test than shown at the factory, where the 
samples are usually weighed and more carefully read. 

During the past year the creamery companies that have kept any 
records of their work have been cutting down this difference between 
tests and helping to correct the low churn results. It is hoped that 
the ideas given in this bulletin will be of some benefit to them; also 
to others who have not realized the possible loss along this line and 
the great probability that they have sustained it, although ignorant 
of the fact. 

SUMMARY. 

CONDENSED DIRECTIONS FOR MAKING: FAT TESTS OF CREAM. 

Sampling : 

(1) Uniform composition and texture of cream is necessary. 

(2) This is obtained by pouring from one pail or can to another. 

(3) Frozen cream must be thawed before it can be sampled. 

(4) Churned cream can not be successfully sampled. 

(5) The tube sampler gives surest results. 

(6) The dipper sampler does well if the cream is thoroughly 

mixed. 

(7) Cream adhering to outside of tube should not get into sam- 

ple jar. 

(8) The tube should be blown out with steam or rinsed with hot 

water before using each time. 
.(9) Keep the top of the tube open while it goes down, so it may 
fill as fast as lowered. 

Keeping the samples: 

(1) Sample jars must have tight-fitting covers and be kept tight. 

(2) If cream is dried in bottles it is evidence that covers are not 

tight enough to prevent escape of moisture. 

(3) Preservatives must be thoroughly mixed with cream; if too 

thick, heat the jars. 

(4) Do not shake the bottle to mix the cream; give it a rotary 

motion. 

(5) It is best to have samples protected from extreme heat or cold. 

(6) Churned cream gives only approximate results; dried cream 

gives too high results. 

(7) Extreme hot weather and lack of attention may cause sepa- 

ration of whey. 

(8) Do not take too large samples; it is a waste of cream. 

(9) Look after samples every day and see that they are in proper 

shape. 



fat testing of cream by babcock method. 27 

Preparing sample for measuring into test bottle: 

(1) Sample must be absolutely uniform throughout. 

(2) Heat sample to about 100° F., or until it is quite fluid. 

(3) If sample is weighed, a much higher temperature may be 

used. 

(4) Pour from one cup to another until uniform. 

(5) The hotter the sample the more fluid it will be and the easier 

to make uniform. 

(6) Take care that no cream remains in sample jar adhering to 

the sides. 

(7) If sample is lumpy, press lumps through a fine wire sieve 

(such as is used for a teapot strainer). 

(8) Melt any churned samples, mix, and sample quickly. 

(9) Make things convenient for this work and see that it is 

thoroughly done. 

Measuring into test bottle: 

(1) Weighing the sample is the only method that wiil give cor- 

rect results. 

(2) Use delicate balances and keep them in perfect order. 

(3) Test weights and scales for accuracj^ before using. 

(I) Torsion balances are very accurate; weigh one test at a time. 

(5) Less than 9 grams may be used, but 9 or 18 grams are more 

convenient. 

(6) Air and gas bubbles in cream cause pipette tests to be inac- 

curate. 

(7) Specific gravity of cream causes pipette tests of cream to be 

too low. 

(8) Tables for correcting specific gravity are in use, but they do 

not correct for error caused by air and gas. 

(9) Weighing corrects all difficulties due to specific gravity and 

air or gas in cream. 

(10) Use great care to get the weights exactly right. 

Making the test: 

(1) If 18 grams of cream are used, add an equal weight of acid of 

1.82 to 1.83 specific gravity. 

(2) If 9 grams of cream are used, add an equal amount of water, 

then add acid as for 18 grams. 

(3) Use enough acid to make a clear fat column; determine by 

trial. 

(4) Use condensed steam or rain water for filling bottles. 

(5) After adding acid, fill bottles at once to bottom of neck with 

water at about 120° F., and then whirl five minutes. 

(6) Then add water of same temperature to bring fat within 

scale, and whirl two minutes. 

(7) Keep the temperature down to 120° F. while whirling. 



28 BUREAU OF ANIMAL INDUSTRY. 

Making the test — Continued. 

(8) Have a hole drilled in top of tester to insert thermometer. 

(9) Run the tester at as high speed as bottles will stand. 

(10) For hand tester put in boiling water when beginning the test 

till it nearly reaches the bottles. 

(11) For steam tester raise the lid slightly while making the test. 

(12) When through whirling keep tester closed, so as to main- 

tain heat even as possible. 

Reading the test: 

(1) See that line between fat and water is straight, and read 

from bottom to extreme top of fat column. 

(2) Read the depth of meniscus and deduct four-fifths of it from 

previous reading. A careful operator can estimate this. 

(3) Add 0.2 per cent to the result. 

(4) For 9-gram sample, double reading before adding 0.2 per 

cent. 

(5) Read at a temperature close to 120° F. 

(6) If bottles are placed in bath to regulate temperature, allow 

them to stand for fifteen minutes before reading. 

The test bottles: 

(1) Use as narrow-necked bottles as possible, to get wide divisions 

of scale. 

(2) The 30 per cent 9-inch bottles graduated to 0.2 per cent are 

most accurate. 

(3) Use 9-gram charge with these, doubling the reading. 

(4) The 50 per cent 9-inch bottles are next in accuracy, graduated 

to 0.5 per cent. 

(5) The 30 per cent, 40 per cent, and 50 per cent 6-inch bottles 

are too inaccurate in results. 

(6) In wide necks the scale divisions are too close together and 

errors are more probable. 

(7) All bottles should be tested for correctness of calibration. 

(8) With cheap bottles nearl} T half are not correct. 

(9) Bottles guaranteed correct can not all be depended upon. 

CONCLUDING NOTES. 

Little more need be said except that there is still much work to be 
done to make a perfect cream test, free from the objections noted in 
this bulletin. The subject of preservatives for composite samples 
of cream is one that needs the attention of the chemists. A test bot- 
tle that will overcome the objectionable features noted is a study for 
some genius to work uj)on. A bottle of uniform diameter would 
greatly simplify matters as they stand, so that a uniform correction 
could be made for all tests. The great importance of careful work 
in all details should be urged upon every user of the test. The 
amount of butter fat that may adhere to the bottle and remain below 



FAT TESTING OF CREAM, BY BABCOCK METHOD. 29 

the neck should be studied and a large number of experiments made 
to determine the facts in the case. The common defects observed in 
field work were improper sampling, poor sample jars, the pipette 
method used in measuring samples, the test read too high and at too 
high temperature, and carelessness all along the line. 

The question of overrun, while in very close touch with and influ- 
enced by the test, is not all dependent upon it. Losses occur due to 
careless weighing of cream, guessing at the weight of cans, leaving 
cream in cans while emptying, losses by spilling, and losses in ship- 
ping. The greatest factor of all influencing the overrun may be found 
in the churning and working of the butter. The question under dis- 
cussion must not be lost sight of, however. Table X is food for reflec- 
tion along this line. The just distribution of money to patrons and 
the financial results of the creamery industry in the West call for 
more careful consideration of this question of the cream test. 



o 



LBFe'07 







i 



